In recent years, an organic thin-film transistor employing an organic semiconducting compound as a semiconductor channel has been studied. The organic semiconducting compound is easy in processing and high affinity to a plastic sheet support, as compared with an inorganic semiconducting compound, and therefore, is preferred in its application to a thin-film device.
There is, for example, description in Japanese Patent O.P.I. Publication Nos. 9-232589 and 7-206599 that an orientation film increases carrier mobility in an organic semiconductor layer.
Further, there is proposed technique in WO 0079617 that mobility of an organic semiconductor channel is increased by orientation treatment of the semiconductor which employs mesomorphism produced on heating a semiconducting polymer to not less than the a temperature providing liquid phase and an adjoining orientation film.
However, the technique proposed in the patent document requires high temperature of at least 250° C. in order to transit the semiconducting polymer to a liquid phase, and therefore, requires, as a support, colored heat resistant films such as polyimide film or heat resistant materials such as glass plates. Further, this requires a process of forming an orientation film adjacent to the semiconductor layer, which complicates constitution of a semiconductor element.
A modified FET structure has been proposed in Japanese Patent O.P.I. Publication No. 2000-260999, which employs an organic-inorganic hybrid material as a semiconductor channel. Typically, a semiconductor element with high mobility is proposed which employs a self-organizing (self-assemble) semiconductor material, which actually requires complex processes to prepare the semiconductor material.